Electroless Ag Research Articles

Controlled Interphase in Carbon Fiber/Epoxy Composites by Molecular Self-Assembly Method

In this paper, a new method based on molecular self-assembly on carbon fiber surface was proposed for the improvement of interfacial properties between fiber and epoxy matrix in a composite system. In order to obtain the controlled interphase, the surface of carbon fibers was first metallized by electroless Ag plating, then was reacted with terminally functionized alkanethiols or aromatic thiols to form Ag-thiolate thin films, which further reacted with epoxy resin to generate a strong adhesion interface. The composition, structure and the morphology of the modified carbon fiber surface were examined by X-ray photoelectron spectroscopy (XPS), surface-enhanced Raman scattering (SERS) and atomic force microscope (AFM), respectively. The results showed that these self-assembly molecules were chemisorbed onto the carbon fiber surface coated with silver via the strong S-Ag bond. In addition, these thiol molecules act as coupling agents between the epoxy matrix and carbon fiber through active functional end-groups, such as –OH, -NH2. The interfacial shear strength (IFSS) of the microcomposites after introduced the controlled interphase using the microbond testing was improved.

Spatially defined silver mirror reaction on a micropatterned aldehyde-terminated self-assembled monolayer

A simple microfabrication technique for silver (Ag) based on spatially defined silver mirror reaction using a photolithographically micropatterned aldehyde (CHO)-terminated self-assembled monolayer (SAM) is proposed. First, both a Si substrate covered with native oxide and a quartz glass plate were exposed to a vapor of triethoxysilylundecanal (TESUD) diluted with absolute toluene for 3 h at 403 K. This vapor phase treatment produced a 1.2-nm-thick TESUD-SAM with a flat, homogeneous surface. Several samples were then photolithographically micropatterned using an excimer lamp radiating 172 nm vacuum ultraviolet light, and subsequently employed as templates for area-selective electroless Ag plating. Optical microscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) confirmed that Ag metal was preferentially deposited on the CHO-terminated regions, resulting in the formation of well-ordered Ag microstructures composed of rectangular 5 μm × 25 μm features. The CHO terminal groups of the TESUD-SAM were found to be effective in reducing Ag ionic species at the solid/liquid interface.

Controlled interface between carbon fiber and epoxy by molecular self-assembly method

In this paper, a new treatment method based on molecular self-assembly on carbon fiber surface was proposed for obtaining a controlled interface between carbon fiber and epoxy matrix in composite system. To form the controlled interfacial region, the surfaces of carbon fibers were first metallized by electroless Ag plating, then were reacted with a series of thiols (different chain lengths and terminally functional groups) to form self-assembly monolayers (SAMs), which further reacted with epoxy resin to generate a strong adhesion interface. The morphology, structure and composition of untreated and treated carbon fiber surface were investigated by atomic force microscope (AFM), surface-enhanced Raman scattering spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS), respectively. SERS study showed that thiols chemisorbed on Ag/carbon fiber in the form of thiolate species via the strong S–Ag coordinative bond. XPS study further confirmed the chemisorption by an S 2p 3/2 component observed at 162.2 eV. The binding energy was characteristic of silver thiolate. The interfacial shear strength of the carbon fiber/epoxy microcomposites was evaluated by the microbond technique. The results showed that there was a direct effect of the interfacial parameters changes such as chain lengths and surface functional groups on the fiber/matrix adhesion.

Electroless deposition of Ag onto p-Si(100) surface under the condition of the centrifugal fields

A novel method of silver electroless deposition on p-Si(100) wafer under the condition of the centrifugal force was developed. The Ag seed layer was firstly prepared on the wafer in a solution of 0.005 mol/l AgNO 3 + 0.06 mol/l HF then the silver film was electrolessly deposited in another electroless Ag bath under the centrifugal fields. The morphology of the prepared silver film was characterized by atomic force microscopy. The crystal orientation of the film was characterized by X-ray diffraction. The experiment results show that the silver film obtained under the condition of the strong centrifugal force is smoother and denser.

Annealing influence on electrical transport mechanism of electroless deposited very thin Ag(W) films

Morphology and conductivity ( σ) of the non-tarnishing electroless Ag(W) films for interconnect were studied as a function of thickness ( d) by Atomic Force Microscopy (AFM) and Tunneling Atomic Force Microscopy methods. For d ≤ 100 nm the conductivity dependence on thickness can be modeled as percolation of the electrical transport while for thicker d > 100 nm layers it was independent on d ( σ = σ 0). A simple electrical circuit model that described the experimental dependence σ( d) for both thin and thick layers was proposed. The AFM study has shown that the small network changes in the film morphology, due to vacuum annealing cause the significant (few orders of magnitude) improvements in electrical conductivity. Although, near bulk conductivity was achieved for the thicker sample, vacuum annealing was not sufficient to achieve such conductivity for very thin Ag(W) films.

Electroless deposition of Ag on Pd-activated TiN/p-Si(100) substrate

Nano-thick Ag films were electrolessly deposited on TiN/p-Si(100) substrates. The substrates were prepared by sputtering TiN on p-Si(100) wafers. An activation process of the substrates was performed by immersing the substrates in a solution of 0.0019 moL L-1 PdCl2+0.45 moL L-1 HF+8.7 moL L-1 aceticacid+0.036 moL L-1 HCl so as to obtain the Pd seed layer. The general composition of the electroless Ag bath was 0.0032 moL L-1 AgNO3+2.24 moL L-1 NH3+0.56 moL L-1 aceticacid+0.1 moL L-1 NH2NH2 at pH 10.2. The morphologies of the Pd seed layer and the Ag films were characterized by atomic force microscopy (AFM). The effect of the Pd activation on electroless Ag deposition was tested by open circuit potential with time technology (OCP-t). For comparison, the morphology of the films deposited by electrochemical deposition on the substrates was also studied by AFM.

The Inhibition of Silver Agglomeration by Gold Activation in Silver Electroless Plating

In Ag electroless plating, Ag agglomeration has been the obstacle to obtain thin Ag films. The crystallographic misfit between the substrate and Ag can accelerate Ag agglomeration. In this paper, Au, whose crystallographic characteristics are similar with those of Ag, is used as the activation material. As a result, the Ag layer was deposited in the form of layer-by-layer growth. Therefore, Ag film electrolessly deposited on a substrate activated by Au can be used to manufacture the interconnections in microelectronic devices. In this experiment, the resistivity of the Ag film was measured to , which was decreased to by the annealing process.

Electrically Anisotropic Thin Films Consisting of Polymeric and Metallic Nanolayers from Self-Assembled Lamellae of Diblock Copolymers

We demonstrated the fabrication of electrically anisotropic thin films of alternating polymeric layers and metallic layers in nanometer thickness by utilizing self-assembled nanodomains of symmetric diblock copolymers. Nanometer-thick metal layers macroscopically parallel to the film plane were synthesized by electroless Ag deposition on Au nanoparticles selectively in one of the blocks. Every Ag/Au layer was completely separated by nanometer-thick polymer layers in the direction perpendicular to the film plane. Therefore, the conductivity of the film was highly anisotropic, differing by at least 8 orders of magnitude in directions parallel and perpendicular to the film plane, even though the in-plane conductivity (2.8 x10(-6) S/cm) was in the range of semiconductors. If self-assembled nanodomains of diblock copolymers were not employed, a serial layer-by-layer process for each layer would be required to fabricate such an electrically anisotropic thin film.

Electrical resistivity of thin electroless Ag–W films for metallization

It is shown that optimization of the electroless deposition and the use of vacuum annealing yield dramatic decrease in the resistivity and its scatter in 100- and 50-nm silver–tungsten (Ag–W) films. Physical processes, which control the resistivity drop during low-temperature annealing and the residue resistivity in the annealed films are discussed.

Characterization of the Initial Growth Stages of Electroless Ag(W) Films Deposited on Si(100)

Scanning tunneling microscopy (STM), high resolution scanning electron microscopy, and transmission electron microscopy (TEM) have been used to study the film evolution at the initial stage of deposition and the structure of electrolessly deposited silver films that contain tungsten [Ag(W)] on single crystal silicon (100). We present the surface covering process at the initial stage of electroless deposition. The surface reconstruction in this case takes place at room temperature. The state and position of the tungsten was also investigated; TEM measurements indicate that is present in the film. STM images of the Ag(W) film growth show a spiral feature that may reveal a dominant electrochemical driving force during the crystal growth. The presence of well-resolved steps in the deposition process and its electrochemical nature were demonstrated by fast immersion chronovoltametry. This method was also applied to follow the changes in the surface energy, which were caused by the surface pretreatment processes and the deposition process itself. © 2001 The Electrochemical Society. All rights reserved.

Selective metal deposition on metal-semiconductor nanostructures

Photostimulated selective electroless Ag and Cu deposition was investigated on thin TiO 2 films doped with small Ag particles and Pbl 2 films doped with Cu particles. The activation that is characteristic of the thin film structures at the electroless deposition was compared to the opposite effect of illumination in Zn vapour condensation.

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Electroless Ag plating was investigated as a method of coating of Al2O3 ceramics with YBCO superconducting oxides. The adhesion strength of the Ag plating increased greatly when the ceramics were pretreated by both mechanical and chemical etchings. From a study on the electrophoretic deposition of superconducting oxides particles from acetone baths, it was found that the amount of deposit increases with the I2 and H2O content of the bath, but excessive addition of I2 or H2O caused an increase in bath conductivity and electrolytic current, resulting in significant hydrogen evolution and a decrease in deposition.After electrophoretic deposition of the superconducting oxides on the ceramics, the ceramics were heat-treated at 940°C for 6h and at 450°C for 4h. The oxide coating was found to be smooth, uniform, and adhesive, and the superconducting properties of the coating were fully verified by X-ray diffraction, diamagentic measurement, and measurement of resistivity.Moreover, coil of Ag wire (φ0.7mm) was completely coated with superconducting oxides just like as above. These facts confirmed that electrophoretic deposition is an effective method for the preparation of superconducting oxides on various substrates of various shapes.